The basic mechanism underlying the intracellular transport of formed cellular inclusions is still disputed. This proposal attempts to determine whether the generation of the motive force is associated with microtubules or with actomyosin. The experiments will involve a combination of new and old technologies, including light and electron microscopy, microinjection, microsurgery, and stereo high voltage electron microscopy. Pigment cells of teleost fish will be used as a model system to determine the importance of the microtubule organizing center and of microtubule assembly/disassembly for ordered pigment granule movements. An antibody will be prepared against the dynein-like protein present in dogfish brain, and this antibody will be used in immunocytochemical studies on isolated pigment cells. Microinjection of inhibitors of the dynein ATPase activity will be employed as a functional test for a dyein-like component in intracellular transport. The same approach, microinjection, will be used to introduce probes that interfere with the state of actin in the cell. A permeabilized cell model will be developed to study regulatory mechanisms of motility in pigment cells. cultured mammalian cells will be used as a model system to correlate the movement of Rhodamine 123-labelled mitochrondria and ingested latex beads with cytoskeletal organization. Movements of the respective components will be recorded by light microscopy in selected living cells and subsequently the same cell will be analyzed by immunocytochemistry or stereo high voltage electron microscopy to define the organization of cytoskeletal elements relative to the moving organelle. These basic studies are anticipated to reveal the function of the components involved in the interaction with the transported organelle and the control mechanisms underlying the regulation of this interaction.